As described in the Non-Patent Documents 1 and 2 as given below, an architecture shown in FIG. 15 is proposed as a configuration of the next generation network of 3rd Generation Partnership Project (3GPP; registered trademark). In FIG. 15, user equipments (hereinafter referred as “UE” or “UEs”) UE 101 and UE 102 are connected to base stations E-Nodes B (Evolved Nodes 13) 103 and 104 respectively via radio wave. Further, the base stations 103 and 104 are connected to access gateway (ACGW; or MME/UPE) 105, which is a control device on network side and connected via wired means. ACGW 105 performs user authentication processing by using a user authentication device 106, and it is judged whether UE 101 and UE 102 should be connected to the network or not. Also, by using a charging control device 107, various types of information including the conditions of use such as the amount of packets for charging the fees to UE 101 and UE 102 (PCRF; Policy Control and Charging Rules Function) are collected. Also, the data of user plane is encrypted between ACGW 105 on one side and UE 101 and UE 102 on the other side respectively.
First, description will be given on a flow of packets between UE 101 and UE 102. The transmitting side UE 101 generates packets to be transmitted to the receiving side UE 102. The generated packets are encrypted to ACGW 105, and the encrypted packet is transmitted to ACGW 105. When the transmitting side UE 101 transmits the encrypted packet, the base station 103 receives the encrypted packet from UE 101 and transfers it to ACGW 105. ACGW 105 receives the encrypted packet from UE 101 and decrypts the packet. Further, ACGW 105 encrypts the packet addressed to the destination of the packet, i.e. UE 102, and transmits the encrypted packet. The base station 104 receives the encrypted packet from ACGW 105 and transfers it to the receiving side UE 102. The receiving side UE 102 receives the encrypted packet from ACGW 105 and decrypts it, and the packet from the transmitting side UE 101 is processed by the receiving processing. Such is the flow of the packet between UE-UE.
As the prior art of data division, the scalable audio coding as described in the Non-Patent Document 3 and the Patent Document 1 is known, in which sound (audio) signals are divided in bands, and each band is encoded individually.    Non-Patent Document 1: 3GPP (registered trademark) Technical Report 23.882; draft V1.1.0 (2006 April).    Non-Patent Document 2: 3GPP (registered trademark) Technical Report 25.813; V0.9.2 (2006 May).    Non-Patent Document 3: “Wideband Speech Coding Robust against Packet Loss”; Takeshi Mori, et al.; Collection of the Articles presented at the Institute of Electronics, Information and Communication Engineers (IEICE); 2005 July, Vol. J88-DII No. 7, pp. 1103-1113.    Patent document 1: Japanese Patent Application Publication No. 2003-241799 (Abstract)
However, in the flow of packets between UE-UE as described above, if UE 101 (UE1) and UE 102 (UE2) are connected to the same base station 103 as shown in FIG. 1, a packet transmitted by UE 101 flows in the order of UE 101→base station 103→ACGW 105→base station 103→UE 102 [the route (2)]. That is, in the route (2), the data is transferred via a route to and from ACGW 105 and the base station 103. As described above, according to the method of the prior art, when UE 101 and UE 102, which are performing packet communication, are connected to the same base station 103, the network resources between the base station 103 and ACGW 105 are consumed uselessly and cannot be used efficiently. ACGW 105 performs communication with a multiple of UEs, and the processing to decrypt the packets from UE and the processing to encrypt the packet to be transferred must be carried out, and a problem arises that much burden is placed on ACGW 105.
Incidentally, when UE 101 and UE 102 are connected to the same base station 103 as shown in FIG. 1, a route can be conceived, by which the packet is transmitted to and from the base station 103 and does not pass through ACGW 150 [route (1)]. However, for the purpose of protecting the user data from the attacks such as lawful interception, encryption must be adopted on the devices at the positions closer to the new network from E-Node B, i.e. between UE and ACGW. Also, for the purpose of communication control, e.g. for the purpose of charging the fees on user data on the network side, operators may require to count the number of packets on the devices closer to the network side or may require to perform lawful interception when necessary. It is difficult to meet such demands by the method as described above.